Optical MEM devices are used to modulate one or more wavelengths of light. Optical MEM devices can have applications in display, print and electrical device technologies. Examples of optical MEM devices which utilize suspended micro-ribbon structures to modulate light are disclosed in the U.S. Pat. Nos. 5,311,360, 5,841,579 and 5,808,797, all issued to Bloom et al., the contents of which are hereby incorporated by reference.
Briefly, an optical MEM device described in the above referenced patents has one or more sets of movable ribbons that comprise a support layer and a reflective top-layer. The support layer is preferably a silicon nitride layer and the reflective toplayer is preferably an aluminum layer. The ribbon structures are typically secured to a substrate through opposite ends of the ribbon, whereby center portions of the ribbons, referred to herein as the active portions, move up and down to modulate an incident light source.
The optical MEM devices described above, and methods for making the same, suffer from several shortcomings. Firstly, fabrication can involve numerous time consuming steps, raising the cost of the devices. Secondly, the dielectric materials typically used to fabricate these devices (silicon nitride and silicon oxide) result in devices which exhibit a propensity to charge. Charging can perturb or shift the switching bias voltage required to operate the devices possibly leading to unreliable or irreproducible optical signals. Thirdly, fabrication steps of these devices are often incompatible with materials and/or fabrication steps used to make integrated circuits. Accordingly, optical MEM devices and integrated circuits generally need to be fabricated separately and then laboriously combined in subsequent steps.
What is desired is an optical MEM device which exhibits reduced charging characteristics and which can be fabricated with fewer processing steps. Further what is desired is a method of fabricating optical MEM devices which can be compatible with standard (complementary metal oxide semiconductor) CMOS materials and/or (integrated circuit) IC wafer processing.